I have been using the white coarse discs basically my whole
career. Now Moore's don't make them and are now supplying a thick
and non flexible replacement which is awful.

Make some cuts, say 4 from the outside of the dist to the middle. Im
assuming you have the ones with the brass center. It will become
more flexible the more cuts you put in there. It doesnt add to the
longevity of the disk tho.

Armstrong hardware co. sells boxes of 50 for $5.50 USD. Many dental
supply's carry them too. Have you talked to E. C.Moore co. because I
have found them everywhere I've looked and find it hard to believe
they aren't being produced with the abundance available on line
only. rer